What is influenza?
Influenza, more commonly called the flu, is a contagious respiratory disease caused by a virus. Most healthy people will recover from the flu on their own within one or two weeks. For the very young, the elderly and people with prior medical conditions, however, influenza can lead to serious or even fatal complications, most commonly pneumonia. The best way to prevent the flu is to receive a yearly flu vaccine – that means every year!
Flu Shot by NIH Image Gallery, available under a Creative Commons Attribution-NonCommercial 2.0 Generic (CC BY-NC 2.0) license, cropped and resized.
What causes influenza?
Influenza is caused by a virus in the respiratory system. When the virus reaches the lungs, the tissues in the respiratory tract become swollen and inflamed. The disease can be passed on to others when an infected person releases the virus into the air through sneezing, coughing or talking. A person might also get flu by touching a surface or object that has flu virus on it and then touching their own mouth, eyes or nose.
Most healthy adults may be able to infect others beginning 1 day before symptoms develop and up to 5-7 days after becoming sick. Some people, especially children and people with weakened immune systems, might be able to infect others for an even longer time.
More than 200,000 people are hospitalized for flu complications each year,and an average of 36,000 people die each year from the flu.
It is estimated that the 2009 H1N1 pandemic resulted in more than 12,000 flu-related deaths in the U.S. In contrast to seasonal flu, nearly 90 percent of the deaths occurred among people younger than 65 years of age.
How can I prevent influenza?
The most effective way to prevent the flu is to receive a yearly flu shot. The flu vaccine contains the specific viruses that are expected to cause illness that year, so it is important to be vaccinated every year. Vaccination generally helps prevent the flu, but it can also decrease the severity of the flu if you do get it.
There are two types of flu vaccines:
- The “flu shot” – an inactivated vaccine (containing killed virus) that is given with a needle. The seasonal flu shot is approved for use in people 6 months of age and older, including healthy people, people with chronic medical conditions and pregnant women.
- The nasal–spray flu vaccine – a vaccine made with live, weakened flu viruses that do not cause the flu. This is approved for use in healthy* people 2-49 years of age who are not pregnant.
The recommendation to not use the nasal spray flu vaccine (LAIV) was renewed for the 2017-2018 season. Only injectable flu shots are recommended for use again this season.
All people over 6 months of age should get a flu vaccine.
Vaccination is especially important for the following people, who are either at a high-risk for influenza complications or come into frequent contact with high-risk individuals:
- Children younger than 5, but especially children younger than 2 years old
- Adults 65 years of age and older
- Pregnant women
- American Indians and Alaskan Natives
- People who have chronic or medical conditions including asthma (even if it’s controlled or mild), chronic lung disease (such as chronic obstructive pulmonary disease COPD and cystic fibrosis), heart disease, kidney disease, blood disorders, diabetes, and/or weakened immune systems.
- People who live in nursing homes and other long-term care facilities
- Health care workers
- Caregivers and household contacts of persons at high risk for complications from the flu
- Caregivers and household contacts of children younger than 5 years of age with particular emphasis on vaccinating contacts of children younger than 6 months of age (children younger than 6 months are at highest risk of flu-related complications but are too young to get vaccinated)
You can also help prevent the spread of the flu by practicing good personal cleanliness. Wash your hands with soap and water often, avoid touching your eyes, mouth and nose, and refrain from sharing drinks or utensils with others. Also, cover your mouth when you cough or sneeze to prevent spreading the virus to others if you are already infected.
Influenza viruses are always changing so it is important to get a flu vaccination every year.
What are the symptoms of influenza?
Influenza symptoms usually come on suddenly. People who have the flu often feel some or all of these symptoms: fever* or feeling feverish/chills, cough, sore throat, runny or stuffy nose, muscle or body aches, headaches, fatigue (tiredness), and some people may have vomiting and diarrhea (though this is more common in children than adults).
It’s important to note that not everyone with flu will have a fever.
Is it a cold or the flu?
Although they are often mistaken for each other, there are some key differences between the common cold and the flu:
|Fever||Rare||Characteristic, high (102-104° F)|
|General aches, pains||Slight||Usual; often severe|
|Fatigue, weakness||Quite mild||Can last up to 2-3 weeks|
|Extreme exhaustion||Never||Early and prominent|
|Chest discomfort, cough||Mild to moderate; hacking cough||Common; can become severe|
How is the flu treated?
If you get sick with flu-like symptoms, you should stay home and avoid contact with other people for at least 24 hours after your fever is gone except to get medical care. Most people with the flu have mild illness and do not need medical care or antiviral drugs. In this case, the best treatment is to rest and drink plenty of fluids.
However, some people are more likely to get flu complications (for example young children, people 65 and older, people with asthma, diabetes or women who are pregnant) and they should talk to a health care provider about whether they need to be examined if they get flu symptoms. Also, it’s possible for healthy people to develop severe illness from the flu so anyone concerned about their illness should consult a health care provider.
While getting a flu vaccine each year is the best way to protect you from flu, there also are drugs that can fight against influenza viruses. These are called “influenza antiviral drugs.” Antiviral drugs are prescription medicines that fight against the flu by keeping flu viruses from reproducing in your body. Antiviral drugs are not sold over-the-counter. It’s very important that antiviral drugs be used early (within the first 2 days of symptoms) to treat people who are very sick (such as those who are hospitalized) or people who are sick with flu symptoms and who are at increased risk of severe flu illness (such as pregnant women, young children, people 65 and older and people with certain chronic health conditions).
For more information, visit the CDC Seasonal Influenza website